Mining Contract: RA Heat Mitigation System Utilizing Advanced Liquid Air Technologies

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Contract #	200-2016-91194
Start Date	9/12/2016
End Date	9/12/2018
Research Concept	As established in previous studies, heat and humidity build-up in refuge alternatives used in underground mines can reach particularly uncomfortable to physically distressing levels for occupants in the event of emergency use. This could lead to the life-saving structures being rated for fewer users. An effective heat and humidity mitigation system will enable miners to use refuge alternatives at their design capacity instead of derating their occupancy, in some cases by as much as half.
Topic Area	Refuge Chambers

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

Per the MINER Act of 2006, all underground coal mines must provide refuge alternatives (RAs) where mine workers can take refuge in the event of an emergency, particularly a mine event in which the air quality becomes so poor as to be potentially fatal without a rescue breathing apparatus. Mine Safety and Health Administration (MSHA) regulations require that RAs (mobile units or built-in-place structures) must be able to sustain life for entrapped miners for up to 96 hours after an emergency event. This includes providing food and water, breathable air, and an environment where the apparent temperature inside the occupied RA does not exceed 35°C (95°F).

While many manufacturers rushed to create possible refuge alternative structures, little effort was expended in proof testing that each refuge alternative would be able to work as designed and meet all MSHA standards. However, that is about to change. Starting in 2018, MSHA will require proof that all RAs meet the apparent temperature criteria for the ambient mine temperatures in which the RA will be located and remain below this level for the full 96 hours.

Research and models show that the relative heat and humidity inside an occupied refuge alternative can climb to especially high levels. For underground coal mines, heat buildup inside an occupied refuge alternative is a serious concern especially where ambient mine temperatures are routinely at or above 24°C (75°F). In addition, relative humidity can approach 100 percent inside an occupied refuge. Without a means to dissipate the heat and humidity generated by the occupants and the carbon dioxide scrubbing system, the temperature and humidity inside such a refuge could lead to severe discomfort, heat stress or worse, depending on the initial inside temperature, which is directly related to the mine ambient temperature.

This contract will design and assemble a liquid air cooling and breathable air system for RAs that will be based on previous research by the company. The system will be tested three times in order to record the system’s effectiveness. The company plans to work toward MSHA certification of the system in order to offer the technology to the industry.